Electron beam oscillator



May 30` 1950 w. w.. HANSEN ET AL Re. 23,234

ELEcTRoN BEAM oscILLAToR 6 Sheets-Sheet l Original Filed Jan. 22, 1958 F/Gl . INVENTORS lA//LL/AM WHA NSE/v RUSSELL/L1'. AH/ N May 30, 1950 w.w. HANSEN rA| Re. 23,234

ELECTRQN BEAM oscILLAToR Original Filed Jan. 22, 193B 6 Sheets-Sheet 2 May 30 1950 w. w. HANsEN ETAL Re. 23,234

ELECTRON BEAM OSCILLATOR Original Filed Jan. 22, 1938 6 Sheets-Sheet 5 D/STA Nef ,x

ATTORNEY.

May 30, 1950 Original Filed Jan. 22, 1938 w. w. HANSEN ETAL Re; 23,234

ELECTRON BEAM OSCILLATOR 6 Sheets-Sheet 4 MM/TER W/LL/AM MAMA/55N May 30, 1950 w. w. HANSEN ETAL Re. 23,234

ELECTRON BEAM OSCILLATOR Original Filed Jan. 22, 1938 6 Sheets-Sheet 5 l" Y f fr f 32 il E 31 f f f dii f ,-,f L:

1/ f ,f 33 if IN VEN TORS WML/AM lA/.HA/VJE/v May 30, 1950 w. w. HANSEN ET AL. Re. 23,234

ELECTRON BEAM oscILLAToR 6 Sheets-Sheet 6 Original Filed Jan. 22, 1938 SMN MNM N A DH m A MHV WH. M L ma. L H U WH Ressued May 30, 1950 ELECTRON BEAM OSCILLATOR William W. Hansen and Russell I-I. Varian, Palo Alto, Calif., assignors to Board of Trustees of the Leland Stanford Junior University, Stanford University, Calif., a corporation of California Original No. 2,269,456, dated January 13, 1942,

Serial No. 186,316, January 22, 1938. Application for reissue ctober 26, 1948, Serial No.

Matter enclosed in heavy brackets Il appears in the original patent but forms n0 part of this reissue specification; matter printed in italics indicates the additions made by reissue 12 Claims.

The present invention relates, generally, to electrical converters or oscillators, and the invention more particularly is concerned with the conversion of the energy of a unidirectional current into the energy of an alternating electro- ;magneti'c eld. Its field of application is principally in the region of frequencies of 108 cycles gper second and higher. It is related to the earller inventions disclosed in copending applicaations: Ser. No. 92,787, filed July 27, 1936, for High .efficiency resonant circuit, W. W. Hansen, Patent No. 2,190,712, and Ser. No. 168,355, filed Octolber 11, 1937, for "Electrical converter, R. H. Narian, now Pate-nt No. 2,242,275.

In Patent No. 2,190,712 for High efliciency ;resonant circuit, there is described a resonant .circuit characterized by an electromagnetic field ibounded by the conducting surfaces of a substantially closed non-radiating container. In this circuit the contained held appears as sus- ,tained standing waves. This is disclosed also fin subsequent cope-nding applications: Ser. No. 3185,382, filed January 17, 1938, now U. S. Patent (2,415,094, for Radio measurement of distances @and velocities, W. W. Hansen and R. H. Varian, Sen No. 193,268, filed March 1, 1938, now U. S. Patent 2,272,165, Electrical converter, W. W. jfHansen, R. H. Varian, and L. M. Applegate, and ,Sen No. 201,898, filed April 14, 1938, now U. S. Patent 2,280,824, Radio transmission and recepttion, W. W. Hansen and R. H. Varian.

In Piatent No. 2,242,275, it is shown how to produce oscillations using an electron beam prol:Iected through two space-resonant devices of the :above-described character, the combination being :referred to as a klystron A k1ystron, in pre- ;ferred form, is an electrical converter and/or amplifier composed of two or more space-reslonant devices excited and coupled by a beam of electrons projected through the electromagnetic :fields contained in the space-resonant devices. We have also referred to the rst space-resonant device in a klystron as a buncher and the ,second as a catchen In the buncher, the electrons are alternately accelerated and decelerated at the frequency of oscillation of the field of the buncher, and in the catcher, the

lenergy of the bunched electron beam is con:-

as an eilicient generator of ultra-high-frequency alternating currents and being capable of deelectrons is adapted to be directed to establishv a standing electromagnetic lield therein, the electrons moving preferably parallel to the electric vector of the eld, which vector preferably varies in intensity throughout the length of the circuit" to effect highly efficient operation, the dimension of said circuit-J along the axis of said beam beingy such as to enable speeded up electrons to overtake slowed down electrons and hence produce groups which are allowed to leave the circuit at lowered velocities, thereby giving up energy to the resonant circuit field and maintaining the same in oscillation.

Still another object of the present invention is to sprovide a novel electrical converter of the above character having such physical configuration as toI enable the maximum possible absorption of energy from the electron stream for maintaining the converter in operation and for supplying any desired load.

Other objects and yadvantages Will become apparent from the specication, taken in connection with the accompanying drawings wherein the invention is embodied in concrete form.

In the drawings:

Fig. 1A is a diagrammatic representation of a klystron Fig. 1B is a graph of certain electric elds relating to Figure 1A.

Fig. 2A is a diagrammatic. representation of our present invention in a form suitable for purposes of explanation.

Fig. 2B is a graph of certain electric fields relating to Figure 2A.

Fig. 3A is a graph of electron velocities plotted with time (t) as abscissa relating to Figure 1A.

Fig. 3B is a graph of electron velocities plotted with time (t) as abscissa relating to Figure 2A.

Fig. 3C is a graph of electron velocities plotted with distance (x) as abscissa relating to Figure 1A.

Fig. 3D is a graph of electron velocities plotted with distance (X) as abscissa relating to Figu re 2A.

Fig. 3E is a graph of distances traversed by certain electrons plotted with time (t) as abscissa relating to Figure 1A.

Fig. 3F is a graph of distances traversed by certain electrons plotted with time (t) as abscissa relating to I ligure 2A.

Fig. 4 1s a' lurvesh'owmg voltage and" current, necessary to start oscillation.

Fig. 5 shows a present preferred form ofem- `5 ttions are started by small departures from unibodiment of our present invention. formity invelocity or density of the electrons Figs. 6A, 6B, 6C and 6D are alternative forms of the beam such as might be accounted for by of our invention. v the shot' effect the electron beam. Energy is Figs. 7A, 7B and 7C are other alternative adaptedfto be" "k'n'ior load purposes from the forms, "lo ,iraiizlier Yspacef vs nflfant device 6 by the coupling Fig. 8 shows another form of the invention. loop I3 or equivalent means, such as capacitive A distinction between the klystron yand the elements. present invention is that infftheqfklystron at fWejwill-not"proceed with the mathematical least two separate electromagnetic `i{j1fds"'a1fe reviewof jthel;lystrn. Let electrons of velocity employed, one for bunching an electron be'arl'i,A lli'vb fror'1""the "`ei`n itte `1` I enter the field between that is, for changing the electron velocitiesgaid. grids! and 5. 4"This iield is an alternating one one vfor caI :ching ,r thatiatalging energy from the and is such that the value of the integral of E bea'rn'; while in'thpresent'inventinvvesafisin v:fornlf` grid Iftofgri'd'l'iis Vr/fyisinfwtfWhere V1 is gle electromagnetic 'field for buncher and catcher the `maximu'rrrcyclic value' ofthevoltage'between and the space in between. Because of this char- 2o grids 'I and 8, 'y is the ratio of the maximum acteristicwwecall {nur present invention the c yclicvalue of the voltage between grids 'I and monotron, that is, a singlqthingf f The name 8v 't o: fthe rn'acii'um cyclic" value ofthe'voltage isproperly usedasianoun molierfsuchoasin between 'gridsf" nd:'5,"JV1/ytis-thef 'stead state the expressions, fmonfotron oscillatolgm n'ioriomaximum val1" i`e o'f voltagejbetvve'e'n` grids d tron detector, et cetera. I n the klystronf os- 5, is then 21 f1vvhre f"`is the' frequency in cycles' cillatolgthetwo spacefresonanty devices are biper second, andti' is timein seconds. Lt-itbe latereuyeupled together by inductive loojpfs or assum-d that Vf/v Lisruchiess than Vnfwnef' other means `In the ,monotron, only onespae- VQ is the v1v o1ta 'g'e of V'therelect'rcns`, that is', "sub-I resonant device is required, inasmuch as only stanti'ally thevoltage '1V oy ""b'att "The Onezelectromeenetie,eld is used'. ,This areln'eje- :ee electrdnyeiocity vdf'ish't co espb 'to the ment '1S O f COUISG Simp1er than the earlier one, leration'yoltag'iVo. The distancei'between thatk of .the klyfitromy but in sorse ways it is gri s 4' aridi is madefif 'infe'xplanatih notso flexible. In general the modes ofapplsinallfcompared with Lthe 'distance'tavrsdfby cetiopendyses f the klifstroh are applica-bie an electrn' ify vieity @monetair-royale. en tothe monotron. 35 electron with velocity vcthattravrsesnthefiield 'rheinonotronis very, simple in its physical betvn-'grilslil and I5T-fallsthrciighrlavoltage embodiment, as. will'beshewngbiltthe methevih-smat Iso-enanas veroeit'y cis-:changedfsay matic'a l considerations linderlyi1g "'it's invention u) "'0+f1fgin @t :Notez mit :sin vwbisfnegatwe and reduction to practice are comparatively 4comh'e tim'lofa'prod. plex. Accordingly,in the pre'seiitdi's'closiire, We 40 the S-bnching procesaffconsider will ,set forth the principalmathematialieaan'elctron-airivingfatgrid If at a time tf. Say tibsliipsnivolvd in 'order that thdsefkled in that it ljefft che g-iidi s at timer; then the ff 1iowthisha'seoffthe ait'olay havefa ba sis Aupon igreltioappn-es; wifi n' to tendu@ tireur-enen investiga-aon -of 1 .1 .1.. v ouh-invention...'.Howevelt, afdiSClCSlirefSilCent 5 A(i) Smm' foi"l the v"prajctical'"lise of "iirj'inifention would not V0+V1 Sm @t y V. requireirnore than a fewdi'egrems ande Simple where-1 'is :the-"distance.'ir'omggrid `5"iam-grinniL @i5 nation. v Diiieirn iatirgi'wefind that if azuniform stream f .the.brelmnafflpat f'fthe mathematical of ANu electrons1-per second-'leaves' grid :f5 the dcrbfifilf'ur Present'inventionfweiwill' re- 50 density,-ariatfaversing:a distance rw-iufbe view shine Vof vthe `thery"o`f the klystron. For this rwe begin withFigure 1A? hifchshows a Rastrea-escalator in-whichs lis-an emitter of 1.1 e 1.s at, electrons, `2 an accelerating battery.YfSi-aispace- Vo v resonant devcerithap'air of'spacedv `grids 4 and 5 5 g: N5W,We-.Seek-.fto.fexpyessfihisa .Four-.ier Sedes, v 5. 5 3' Second spae're-s0n9fnt deve'wtha gud T lnowngfithat'if lwe succeed,:thexpowerlputfint and agrd'or'plee 8 'spaced ihfefmmf 9 and l' the' cirbuit'ffassocia'ted Wahine ...grids i .and's are coupling lOODS CODI'IEteC-byfa palrfof C011- 'c'an-ibe computed in termscfffthej voltageacrofss ductors I2, preferably in vthefiform* offia concen thegds Tandsfand .the-yalueoithe appl-emp tric "une, nd: 13 *is a coupling loop for Output' rate Fourierf'coefcientei-nthe `series for'the 'ciir- Briey, the operation is as follows: A beam I "30 rent 'of electrons/iis projected L from the emitter I Thus Wewrite through the? grids 4 and Eiwhere positive and negative accelerations of electronsin the y i:eeml (2) .a .ucosi'gyyaqfb occur! alternatelyat the natural frequency of the l`-k"cos'wt system. .The electrons leavinggrid 5 travel tofc5 Where ward i grid 'I at differingvelocities so some elec- 1 trons gain on others with the result that at rig- L21 'grid j the; electrons arrive vvinmore or --less clearly "V0 defined surgear .groups .0r buehes, in which ,7o .arid ai is aphaseisna,andrea-timmy@asas/tue individual electrons have velocities varying over a; considerable range. Entering .the field between rgrids vI and YIt the bunches of electro ns periodically deliver pulses of energy tothe electromag- 1 i etio, =i ield, in. t he space-res `tdevice E at its natural frequency,v lthus i eiic1t1n'g"'and Liaitain- '1" ing itin a state of oscillation. Energy for bunching is transferred froiV the' `catche'r spacere'sc i1.'ntA device Beto thefbuncl'i'erfSf bythe coupling loops 9 and I I and line I2. The oscillaof t' rather than t" so we change the variables as follows:

It will be seen presently that bn should be selected to make the constants on the right add to zero. This is physically reasonable since the' phase shift b must be determined by the transit time l/vo. Then wt-}bn=wt'-k sin wt' and dt"=dt (1 -k cos wt).

4) witg n (Dk) where Jn is the Bessel function of order n. The problem is now essentially solved.

To see how this applies in practice let us select a particular case in which a current of electrons I=Noe passes through grids 4 and 5 and iind how much power is transferred to the circuit connected to grids 1 and 8. Suppose the voltage between grids 1 and 8 is kept at a value just sufficient to stop the slowest electrons, that is, Vo-Vi/y. Since we have already made Vi/'y very Small compared with Vo, let us simplify the formulae by taking the voltage across grids 'l and 8 to be Vn. Then the power into the catcher circuit 6 is just VnIJ1(k) This assumes that the second circuit is running at the fundamental frequency. If it were on the nth harmonic J1(k) would be replaced by Jnmk). Since the power expended in accelerating the electrons is VDI the eiiiciency is J1(k). When it is possible the arrangement is designed or adjusted so k will give the maximum efliciency. The best value of k is found from tables to be 1.84 and the corresponding value o- F J1 is 0.582. We have referred to the deceleration of electrons in the catching field as if the action were complete, but a full understanding of the mathematics will indicate that deceleration of all electrons is not practically accomplished. Actually even under supposed optimum adjustments there may be a few electrons accelerated in the catching eld, although most of them will be decelerated as is desired.

The above calculations can also be used to determine the mutual conductance of the klystron used as an amplier. Thus, supposing k is much less than 1.84, we can approximate J1(k) as k/Z and so und for the ratio of rst harmonic electron currents to buncher voltage r11/,sivo with =vuc. This increases indefinitely with l, apparently, but actually an effect due to ele-ctron space charge which we call debunching occurs which prevents utilizing very large values of l. This effect which is the result of mutual repulsion of the electrons when crowded together in the beam tends to limit the sharpness and density of the bunches as the distance traversed increases. However, with moderate values of l useful values of mutual conductance can be attained.

Finally, as to the klystron, we may note that there are three independent parameters adjustable in operation and two that are determined in the design. The rst three are: (1) the initial velocity vu of the electrons; (2) the number per second N of the electrons; and (3) the ratio ry of the voltage between grids 1 and 8 to the voltage between grids 4 and 5. The two design parameters are: (l) the bunching distance l; and (2) the effective shunt impedance of the catcher space-resonant device, i. e., the quotient i obtained by dividing the alternating current voltage generated within the catcher-resonator 6 between grids 1 and 8 thereof, by the alternating current component of the electron stream current passing through this resonator. The latter parameter is often made variable, but it simplifies matters and sacrifices no essential generality to consider it fixed.

We will not proceed to the description of the monotron, one form of which is shown in Fig. 2A, in which 2l is an emitter of electrons, 22 an accelerating potential battery, and 23 an evacuated shell constituting a space-resonant device of special shape. The shell 23 has a bounding surface including apertured grids 24 and 25 in oppositely disposed end faces of the space-resos nant device 23. By `comparison with the klystron of Fig. 1A, it will be seen that the two Spaceresonant devices 3 and 6 and the associated coupling loops 9 and Il have been replaced by a single body 23 in Fig. 2A. The electron stream from the emitter 2l has a substantially uniform distributio-n in time outside the resonator 23. In operation, the space-resonant device 23 contains a conned resonant oscillating electromagnetic eld with a substantial magnetic eld component .and having standing waves. The electric field ycomponent extends along the axis of device 23, i. e., from the center of grid 24 to the center of grid 25, and its magnitude is E(x) cos wt with E as represented in Fig. 2B, in which E is the electric field strength within container 23 along the axis of the electric field component and also along the axis of the electron beam projected through member 23, x being the distance from grid 24 toward grid 25. The cavity resonator 23 may also be constructed so as to support a direct current field, but this possibility Will be neglected for the moment. As will develop presently, the exact shape of the curve for Elx) along the path of the beam is unimportant-all we need to know when carrying out a sample calculation is that it has no discontinuities, i. e. sudden changes in the value of the electric field component and this is true as long as there are no conductors on the axis inside the space-resonant device. Actually the device will operate with discontinuities in the electric field vector, such as those caused by conductors, but such forms of the invention require more complicated calculations which will not be given here. A distinction between the arrangement shown in Fig. 1A and that shown in Fig. 2A is that in the rst the ratio of the Voltage drops in the electric vector extending between the grids 4 and 5 and between grids 'l and 8 was adjustable while in the second a corresponding ratio exists in theA field strengths adjacent the grids 24 and 25, but

in the .case of Fig. '2A this ratio is determined by the design. Thus the three adjustable parameters, i. e. accelerating voltage, back-coupling and current, in the klystron are reduced to two, i. e. accelerating voltage and current, in the monotron and the number dependent upon the des-ign are increased by one in the monotron.

Thus, the simplification of design sacrifices the reference may be made to Figs. 3A to 3F, where-V internally resonant conducting hollow.

electrons beforetheyV enter the spacefbetwe'eri gridsV 4. and', being'thus indicative of.' the fact that both, electronsjhavethe .saine velocity duringthi'sintial period.. The electron represented bythe'dottedfline90, leaving cathode I ea'rlien reaches. the interspace between grids 4 and "5 rst, and assumingv that theinstan'taneous electric'jield Vin the interspacey opposes this electron, it smovement willbe retarded, as represented bythe dotted line S2'. bythe solid liney 9'! reaches the. interspace a halfc'ycle later when theV eld therein is reversed, and henle the :Field accelerates 'this electron; as represented bythe fulljlne 93'. After leaving the grid. 5; and by the' time the electrons reach the interspace. between the Vgrids land' 8, the speeded-up electron representedV by thev solid line has overtaken at Si the slowed-up electron', represented by the dottedline 92. The portions of the paths of these electrons between the grids 4 and 5 .are omitted for purposes of simplification,

There two electrons are representative of' a group that 'is 'thus formed, upon entering the interspacebetween the grids l, and-8: this' interspace the group or'bunch of electrons isadapted to be subjected toanalternating electric eld. If the phase of this field' is'such as to oppose the electron bunches, the electrons of the bunchesV will be slowed down, -and the kinetic energy thus lost by the electrons will evidentlythen beY transferred, to this 'electric held. One half-cycle later; theY electric field will be directed so asto speed up electrons passing between grids 1" and 8, but at this time there are fewer elec-v trons passing between these grids since this portion of the electron-beam has been rareed due tothe bunching operation, with the resultthat the eld does not lose as much energy to these b fewer electrons as it gained from the ,relativelyl greater number of bunched electrons passing through during the previous half-cycle, and

hence, becauseof the net energy-supplied to them, the oscillations in resonant circuit member of Fig. 1A Awill tend to increase in amplitude. Consequently,l all that is required initiallykv is a yvery small transient oscillation, no matter how in' eiitractedwherefrom. Thus,' the deviceof Fig.'

1A becomes a self-excited oscillator.

1n' Fig. 3A, 'the velocities of the two electrons are plotted as a'function oftime. The-electron illustrated by the dotte'd'line 9D `enters the interspacebetween the grids `4 and 5 when'theeld opposes "its motion and'has its velocity: v re-r duced as sho'wn'by the downward Aslopeifot-this' dotted' line 90, and 'thereafter i-ttravels vmore slowly. 'I'he electron 'illustrated bytheA solidline enters "the finterspace'- 4 5-15'V rvlaterywheny the fieldY The electron represented aids;itsmptiemand.heneinneases. nivelacity as' shown by the upward slope of' this solidw line,

9L This electron, represented by the full line 9|, althoughwleaying the interspace 4,-5 later than the electron represented by theV dotted line 9|),A nevertheless overtakesrthe. latter at the timey it rieacliesthe` interspace between .the grids 'll and; 8,. Both electrons,` after., travelingbetween,A thelz'grids-r--55and 1, as. represented at 92:, and 9,3,

respectiyely, reciyesubstantially a reduction in velocity in passing through. therv opposingv field;A extending between` thegrids'l and 8, which may bevery large. relativeI tothe changes in velocityy of the original energy given tothe electrons by z an electron bunch orfgroupsimiiar'to the bu h orfgroup found -inthe klystron upon-enter ng- "f1 erably less than this.

the accelerating eld of the energy source comprising the battery 2 may be transferred to the oscillatory'ield in rthe catcher resonator V6.

In Fig. 3F, correspondingl to the operation of:v the lInonotron structure. of Fig. 2A, it will at present be assumed'for purposes of explanation; thatthe alternating electricfeld extending between the gridsI 224' and" 25i is uniform in space. Then, ifr the electron representedfby the dotted line 96` enters the space between the gridsV 24- and 25Jwith velocityv at a timewheriithe. eld. within thisfspaceis"ze1o and about `to increase in a direction to .opposeA the motion of thev electron, the latter; laits/further travel in. the eld, will belslowed down for the ifirst half-.cycle of oscillation.'o'thefiield as' represented at Sl', andA will' be speededfup, as indicated at 53, in its passage duringfthe secondhal-cycle; so 4"that at the. end"of"the2fullcycle; it will have the samevelo'cityl at 992 as" that withfwhich" it entered. the space. During'the remainder ofY the time that ths'eleCtroni isi -in'fthe interspace between,y the grids 24 and-'25; its velocity willbe 'decreased' due to-the'reversal -ofvfel'd sov that by the time it leaves: thevgrid'k 25 its velocity is below that at whicliitentered the grid 2t'. wasy initially: slowed downupon its entry? into..thel eld 'ofV resonator-23', rits: average velocity therein isf'below'that-fwhich lisgfpossessed at its time of I entry, if: e:below vo.

Similar reasoning :will show that the electron represented 4bythe solid line |20!! entering later and atthe beginnngf'or'the reverse halfecycle will have an averageV velocitywithin the space *between the 'grids '24and' y25j that is greater thank the space between the .grids i and a thereof. now;fthisfgroupleavesfthe electric held through the `grid 215 atatime when all the electronsin =the havaminimum velocities, the fastest.

electrons oij-the-.group will4 have a velocity ofabout` ,g .the electric vector yto be of:` uniform" etrexigtfor` allffvaluges of whereasthe slQLweS-telectrons--wilgl` have a velocity consid- Though the electrons, have beth-samerenerfsy from and I `10st' enersvf tothe fleldduring-their travel. therethrough, therefore,

thefgroup-as afWhQle, by thetimethat theA elec-v l maintain the field-.that :is tqsupply .all glosses-,

and to feffectblinchins of the. electrons. the devicefwili, est asa self-oscillator.

Since this electron If desired, the proportions of the resonator 23 and the frequency of the oscillation may be made such that the electron remains for a longer period within the resonator, but the net result will be the same so long as the electrons leave the resonator at reduced velocities. In this event, the second and subsequent cycles will be a repetition of the changes brought about during the first cycle.

In the device of Figs. 2A and 2B, the electric field increases in strength progressively along the axis from the grid 24 toward the grid 25, as described hereinafter in connection with Fig. 6C. The dotted-line electron that loses energy in the first half-cycle, therefore, does not al- Ways have its initial energy or less, as in the case just considered. This will be understood from the description hereinafter of Fig. 3B. Nevertheless, it is still true that the electrons that have been slowed down in their first halfcycle in the interspace between the grids 24 and 25, will have less average velocity throughout the remainder of their passage through this space than those that are speeded up in their first half-cycle, and so bunching of course occurs, and with the bunches passing through the grid 25 when they have minimum velocity, they will deliver energy to the field existing between the grids.

It will be recalled that in the initial discussion in which the electric field was considered uniform between the grids 24 and 25, the faster electrons, in passing out of the eld through the grid 25, delivered only the energy they had received in the first half-cycle after they entered through the grid 24, and hence these electrons contributed nothing to the energy of the field. If, however, as shown in Fig. 6C, the field increases in strength between the grid 24 and the grid 25, which is true of the structure shown in Fig. 2A, as hereinafter explained, energy may be extracted from both the fast as well as the slow electrons, for all electrons of the bunch will leave through the grid 25 with less energy than nthat with which they entered the grid 24. Hence, a device in which the field increases along the length of the resonant circuit, as shown, that is, in the direction of the electric field, is a more efficient device than one in which the field is uniform with distance.

Fig. 3C is similar to Fig. 3A except that, instead of the velocity being plotted as a function of time for the electrons in their travel through the oscillator, the velocity is plotted as a function of distance. The dotted line 9U represents an electron that, when entering the space-resonant device 3 at the grid 4 at a certain time, is decelerated. The solid line 9| represents an electron that, when entering the space-resonant device 3 at the grid 4 a half-cycle later, is accelerated. Because the electron represented by the solid line 93 has a higher velocity in the space between the grids and 'I than the electron represented by the dotted line 92, it may reach the grid 'l' at the same time as the electron represented by this dotted line 92. If this is the case, both electrons will suffer approximately the same loss in velocity as represented in Fig. 3C by the sharp drop in both the lines between 1 and 8.

Figs. 3B and 3D hav-e the same significance for the monotron as has been previously stated in connection with Figs. 3A and 3C for the klystron In Fig. 3B, the earlier entering, dotted-line electron enters through the grid 24 at a time when the field in the resonator 23 is l0 l zero and about to oppose the motion of the electron. In the subsequent half-cycle of the resonator 23, therefore, the electron represented by the dotted line is decelerated. In the next halfcycle, the electron is accelerated again and, since the field is increasing in strength from the grid 24 to the grid 25, it will reach a velocity slightly greater than its initial velocity, as shown in Fig. 3B, when it reaches the point 8U. Its velocity will then decrease again, reaching a new low velocity at 8l, from which the velocity will increase 'and reach another high at 82. This will continue until the electron leaves the field at the grid 25.

An electron entering the field one-half cycle later will be accelerated during its first halfcycle in the field and will reach a velocity maximum at the time, corresponding to that of 80. It will then lose velocity, reaching a velocity minimum at the time corresponding to the point 8l. It will then gain velocity, so as to attain a velocity maximum at the time corresponding to the point 82, and will continue, in a similar man'- ner, until it leaves the grid 25 with reduced velocity, as did the dotted-line electron represented in this Fig. 3B.

In Fig. 3B, it will be noted, the electrons ar illustrated as traveling the distance through the resonator 23 in a plurality of cycles, as distinguished from Fig, 3F, in which the electrons travel this distance in something over one cycle.

Fig. 3D is a graph for the monotron corresponding to Fig. 3C for the klystron, the velocities of the electron being plotted as a function of distance. In this case, an electron represented by the dotted line enters through the grid 24 at a time when the field in the monotron is zero and changing in a direction to oppose the motion of the electron. This electron is first slowed down for a half-cycle, so as to reach a minimum velocity at a distance indicated by the point 83. From this point, the electron velocity is increased to a new maximum 84, that is shown somewhat above the initial velocity. In the cycle between the entrance of the electron at the grid 24 and its arrival at the point 84, the average Velocity of the electron has been below its initial velocity. This electron then goes through another cycle of velocity changes between the points 84 and 86, through a minimium 85. In this second cycle, the average velocity of the electron is also below the initial velocity. The electron continues in the same :manner until it reaches the grid 25, Where it leaves the field of the resonator 23 with reduced velocity.

The solid line of Fig. 3D represents an electron that enters the field one-half cycle later than the electron represented by the dotted line, receiving consequently an initial acceleration from the eld, and reaching its first maximum velocity at 87. It then loses velocity, reaching a minimum velocity at 88. In this cycle spent in the resonator 23, the average velocity of the electron was above the velocity with which it entered through the grid 24. Since this electron has traveled faster than the electron represented by the dotted line of this Fig. 3D, the distance along the axis separating the successive maxima and minima of velocity is greater than it was by the electron represented by the dotted line. The point 88, representing the minimum velocity of the electron, therefore, is somewhat farther along the x axis than the point 84, representing the maximum velocity of the electron represented by the dotted line of this Fig. 3D. If this electron is followed through the succeeding cyclesyof itspassage through the resonator '23, it :Will-be -found that, throughout its passage-,vit `maintains a higher average lVelocity than the electron representedpby the dotted line. The points represented rby `successive maximav and minima on this curve Willprogressively'get fartherl and :farther ahead of the corresponding points of the dotted-iine curve until,` when-the electron reaches the regienimmediately infront ofgthe grid :25, it will haye'gainedfone-half,cycle on: the-electron represented vby the-.dotted-line curve, andz-,Willg-'suier -a vlargeloss offveloeity during'vthel half-cycle just. before passing` through the grid 25, the same as was the casevwiththe electron represented I'by the dotted-line curve Whichfentered through the grid 24 one-half cycle earlierf As- Shown,inwligfBD-,ir the distance the electnonsrhavefztraveled is such that the electron represented vby-the vdotted line and :that -representedffby the-solidsfline arrive atv the grid 25 approximatelyl at the same instant; at a` time when'their respective velocities are both atgia minimum.'v vThey will*v thereforel 'have delivered energyitothe.alternatingeld in the resonator 23.

It;.fis.possible,. however, byfslightly changing the evelocities of the i electrons in vtheir, `tr-ansit vfrornthe gridnto-the grid 25', to causethe electrons represented by the full-line curve.: and the"dotted line Curve to arrive together' atathe gri'di25'at`a :time-When, they will have a maximumyinsteadnf a minimum velocity. Under theseoconditions, the electrons of the electron streamywi'll absorb energy from; theresonator Y circuit, instead oivdelivering energy'toitlso that any initial transient oscillations `would die out' instead of-.tieing built-np: intoy steady-state oscillations. This -change of velocityfmay be .effected by a change of voltage applied between the cathode .2 Ii and the grid 24'; By maintaining the. eld of;resonator;l EB-.frOmvsome external. source the electrons may thus. be speeded up.

In' the monotron, however, theY oscillating electrioeld contained in the resonator 23 has a :component atsubstantially all points .of the fieidln substantially the direction of travelof the electron streamvatrcertain times and in substantially ,the opposite direction at other times, dur- .ing alternate half-cycles, Buring their travel through the resonator 2.3,':the electrons interact Witlrrthe yieidof. the resonator at the vresonant frequency of the ield, so that their speed, in the.` direction of travel thereof, becomes increased and decreased, and theelectrons become thus concentrated'in groups in, aregion :of 4the eld priorl tofreachingxthe Vgrid"2'5.. i .Suehi interactionimaybe producedrby, for example, regulatingfthe-a-time'fof flight-.ofthe stream in: the elci; Thefield ofthe resonator is less intense at'itsrboundary adjacent tothe grid v24 than* at itsfbcmndary` adjacentI to the grid 25. Increments andadecrements yof energy offthe period of ,the-neld-are--imparted to thew electrons both nearlv the grid 24; to' cause the electrons to assume-periodically fvarying velocities, and s int a subsequent `region of the iield, but the increments and-.decrements imparted individually to the ,electrorisinA the subsequent regionare greater"than -those imparted to the electrons vat `the grido, with the decrements exceeding the increments; The energyoflthe :groups becomes ultimately absorbed by, or :delivered .toixtheaeld at the Aresonant frequency of the field just before the electrons arrive at; the grid 25. The electrons :"thusdeave vthe 'ield infr the resonator: 23 with less :energy than; theyrhad when r they :enteredf` it and ',electromagnetic; resonance isV f excited and maintained iirtherfleldiat'the resonant frequency of the field to sustain.,v oscillations in the eld.`

The space-resonant device.V 23 is of; such: proportions and Vtheelectrr ns ofzxthe streamithave such velocities as to establish the before described electromagnetic. iieldfthereini Specifically, the dimension ofthe space-resonant device 23 inthe direction/of. travelofthe electron stream; and Ythe resonant 'frequency` of the'eld areso related to the f velocity ofwtheelectron stream inthe space-resonant device23' las to cause: the field to abstract venergyffrom the electron stream.

The portion of the'eldof thezspace-resonator device 23 immediately. adjacentftoithevvdiscontinuity or breakingxoif of the"i field at the grid 24, and-.dueto the presence'thereofperforms the same,` function that A,thegfieldfl-i-betvveen the grids4 and 5 does inxthe k1ys.tron,"and .the

:portion off the neld betweenf tneinside andthe outside of 'the fspace-resonantl device y 23,.,atathe discontinuity immediately adjacent .toV .the grid 25 performs, the samefunction as: the eldbetween grids. .'I and vl? Sintheklystron. Of course,

the field need not be strictly discontinuousia `All that is required is lthat theneldchange greatly inzza space short comparedto'the distance traversed loyvanv electron in,.fsay, onelcycle. t Such a discontinuity is easily producedf at a properly designed grid, Onzthezotherihandgwhat is practically a mathematical.discontinuity in the-field occurs at the iconductingsurfacesr In the space inside the rhumbatron the fieldmayfbe of: high intensitywhereas ,insidefthe conductor at the boundaryof the iieldithe intensityxis nearly zero. Thus',V a discontinuity" in field mightv occur at a grid, or at a .conductingvsurfacd and this` latter might be l a suriace where electrons arrive orit might equally well'be a surfaceV fromwhich they are emitted. The similarity in-"the principles of operation `will "ce-apparent from the mathematicalzconsiderations toibe'presented'.,

If an electron of.y charge -e, enterszfthe first grid 24 at time t.-to, Withl initial velocityvo determine-d bybattery 22, its velocity at any later time t will be Where E is the `Value of E(X) Where the electron is at time t".

Here We could add also-a term to account for va unidirectional fiel-d ,that might be ,superimposed on the oscillating field. For convenience this vflli `be omitted, but-'it will be apparent from va full understanding ofthe theory' that a unidirectional field should be provided for. The essential parts 0f our invention are a unidirectional ield, an oscillating field and a stream of electrons in the oscillating field. Also, asl indicated, the oscillating field must have what amounts to separate field portions adjacent to the twogrids 24 and 25 before-mentionedV for respectively changing the velocity of the electrons to enable them to become grouped and to absorb the energy of the groups. When the adjustments are right, the electrons can effect transfer of energy from the unidirectional eld to the oscillating field. In Fig. 2A, the unidirectional andl oscillating fields are shown separate, vthe unidirectional field'being ybetween 13 the cathode 2| and the grid 24, outside the oscillating field, while the oscillating field is confined in the enclosed space between the grids 24 and 25. In Fig. 5, the elds are shown partly superimposed, the unidirectional field produced by batteries 2| and 35 being between the cathode 25 and the grid 32. In Fig. 8, these fields are completely superimposed.

To resume consideration of Equation 6, E' could, in principle, be found as a function of t and the integration performed. Actually, this would be extremely diflicult to do except in certain special cases. But the information we really need can be obtained, provided E varies slowly enough, by repeated integration by parts. Thus (7) v=vu 6. t=t 01E; '|t: mw{E sin mt ltEtD-I-dww) cos wt tl:

Averaging v over the transit time through the space-resonant device 23, which usually covers several cycles, the terms due to the upper limits practically drop out. The series of lower-limit t l to M terms usually converges rapidly, and in the few cases where it does not, the main results are substantially the same, so we shall drop al1 terms after the rst. The average speed of the electron is therefore eE(O) mm2 Here E(O) is the peak oscillating field intensity at the entrance grid 24. Thus the average veu sin oto `oscillates during the bunching instead of remaining constant as in Figure 1A has no great effect. Referring again to Figure 3D, it will be seen that if grid is moved back toward the origin it will be encountered by the hunched electrons when they have maximum velocity instead of minimum velocity. would take energy away from the field in the space-resonant device 23 and would tend to stop oscillation. This is the condition for accelerating a stream of electrons in a rhumbatron driven by another electron beam or by an outside oscillator. If the grid 25 is moved back to a point where the bunched electrons have maximum velocity, the stream can be also shifted back if desired by increasing the time of transit between grids 24 and 25 by superimposing a unidirectional ield on the alternating eld in the space-resonant device 23, or by changing the field in the space between the cathode 2| and the grid 24. This acts on all the electrons alike and changes their transit time `without greatly changing their iinal velocity. The

Under this condition they llocity of the electrons depends only on their time casu 14 f i stream than is necessary to maintain the small oscillation we have assumed to exist. That this can be the case in this device is about to be shown. The oscillatory field is set up between grids 24 and 25, and is a continuous function of x, i. e., the distance toward grid 25 from grid 24, but drops substantially discontinuously to zero at these two grids, as is shown in Fig. 2B. Through the grids passes a prescribed stream of electrons going at a velocity determined by the voltage of the battery 22. We intend to compute how much alternating current power is delivered to the rhumbatron 23 and what fraction this is of the direct current power supplied to the electron beam. In performing the calculation we will consider as known any needed characteristic of the rhumbatron or of the field produced by it.

To perform the calculation, we proceed as follows. We take the change in average velocity of the electrons from Equation 7 and insert into Equation 4 getting for the peak value of the first harmonic component of current at the second grid IoJ1(k) where Io is the direct current and k=E(O) /2V, where V is the accelerating voltage of battery 22. Likewise, the second harmonic is I02J2(2K) and it will be found that higher terms are not needed.

Next we need to know the maximum energy an electron can transfer to the eld. This will depend on the electron velocity, and on EG) and is found by using (7) to be This equation is correct only when the rst term in the bracket is more than twice the second. Physically this corresponds to the requirement that the electron shall not lose more velocity than it has, that is, it must not be turned back. Of course, the apparatus can be run so that some electrons are turned back but for that case these computations do not apply. Also, it has been assumed that the change in average velocity is small compared to that velocity. The apparatus can run well even though this assumption is not fulfilled.

Now we can compute the total power put into the field by using (8), and the Fourier series for the current, and remembering that not all electrons deliver the maximum energy to the field. On the other hand we will assume that the average transit time is such as to make the electrons deliver as much energy as possible. This condition may be met in practice by adjusting the electron voltage or by adjusting various direct current fields in the rhumbatron or by concurrent adjustment of both. The power so computed is to be equated to the power required to keep the rhumbatron in oscillation. We will take this to be aE2(l) where a depends on the losses and loading of the rhumbatron. That is, c is of dimensions cm.2/ohm and takes into account both the power used in the rhumbatron and the power that may be used usefully. Thus, for any given rhumbatron there exists a minimum a; this may be increased by coupling in a load. We finally find This essentially solves the problem. This is seen when we remember that EKO) and E(l) are re- 15 lated through the characteristics of the rhumloatron so that, given V and Io tvc-have oneequa'- tion to solve for one unknown, say E-(l), and so the power vinto the rhumloatron and the efficiency of the conversion from a unidirectional current to the energy of an oscillating field.

This is not the preferred form*l for solution so a simplification is made and a schemefor calculation introduced. This is done by considering E and V as given and solving (9) for'Io. The efciency is also found in terms of E and V4 and so We can find values of In, V and efficiency that Looking at these formulae We see that if we plot contours of `constant eliciency usin'gI .and u/a2 as variables then We can. use thesame chart for all monotrons, individual differences being taken into account in the factors converting. I and v /aZ into actual amperes and Volts.

We may notice that, for present purposes, three quantities characteristic ofthe rhumbatron are of importance. These `are a=E(l)'/E(O), the ratio of exit to entrance eld strength,.l/ the flight distance of the electrons measured iniwave lengths, and 4f r1/A2, which is a measure fof the energy required to maintain the eldinside the rhumbatron.

An unnecessarily extended discussion Ycouldbe based on Equations l and l1, and ,theirrelation to oscillator eiiciency, modulation, et cetera, and with slight additions ldiscussion couldbe given of regenerative,super-regenerative;.and os cillating-detectors, et cetera. Most of .thiswill be reserved for the future, however, and at the moment we will only'discuss somepoints of immediate interest.

First, we note that the line of zero efficiency bounding the region of oscillations is determined by lettingf O whereupon we nd thatyjust on the edge of oscillation This, according to our computations, is vthe min.-A

16 imum electron current "that will sustain. oscillation ina system to which a given set offdim'ensional factors will apply. From this equation it is evident that a low value of a makes it easy to start oscillation,. though, aswe will see ina moment, it may not lmake it easy to `get high eiliciency.

We may also write down the conditionsk for maximum efficiency. These are found'tobe..

and

These combine to give That `is,.the most eflcient voltage is determined by l/ and Y. From this we see that in order vfor the deviceV to run eiiciently at a .reasonable voltage 'Li l cannot be too small.

The current that goes with maximum eiciency is easilyfound to be and the energy'that may be extracted'from the electron beam in a single transit through` the resonator 23, as above-explained,may be49 per'-i cent.

In computations for the design of the monotron it sometimes happen that E goes to innity at one of the grids. In this case the following theorem due to Bromwich is of use.

Let F(x) be a function of x which has limited total fluctuation when x=0; let Y be a function of v which is such that L17-0 as uw, Then. if -l ,u 1

and, if O u 1 the sines may be replaced by cosines throughout. This may be found in Bromwich, Theory of Infinite Series, paragraph 174.-

Figure 5 shows the' present preferred form of embodiment of our invention. In Figure 5 'there is an emitter 25 from which is accelerated ya stream .of electronsoy the voltage of Aa battery 2|. The electrons enter an evacuated portion .16 of the shell 28 and an evacuated-internal portion 29. At the entrance of shell 213iV there is a grid 3l corresponding to grid 24 in Fig. 2A. The surface .32 which may be either solidk or perforated corresponds to the grid 25 in Fig. 2A. Depending upon the relative proportions of the spherical surfaces 28 and 29 shown in Fig. 5, a field inside may be produced that is more concentrated at the surface 32 thanat grid 3 I This, as is indicated by thecornputations, is desirable in order to. attain high efliciency and ease of starting oscillation with moderate voltages and currents. Thevgeneral configuration of shell 2.8 isr .that of a sphere deformed .inwardly to form the `part 29, as described hereinafter in connec- 17 tion with Fig. 7C. This is also spherical in general and it is supported on a circular conical section 33. The two sections, 28 and 29, are insulated at an annular joint 34 which has a relatively high capacitance between the two sections. Across the insulation of the joint 34 there is the battery 35 which superimposes a unidirectional electric field on the alternating eld of the spaceresonant device. By adjusting the strength of the battery 35, it is possible to adjust the time of flight of the electrons through the evacuated chamber 16 and also to adjust the relative time spent by the electrons in the vicinity of the grid 3| to the time spent by the electrons in the vicinity of the grid 32. It is also possible to adjust the flight time of the electrons in the chamber 16 by means of the battery 2| exactly as described in connection with Fig. 2A, without any change in the relative time spent by the electrons near the grid 3| compared to that spent by the electrons near the grid 32. By independent adjustment of batteries 2| and 35, therefore, it is possible to obtain a desired night time, and also a desired time spent by the electrons in the vicinity of the grid 3| to that spent by the electrons in the vicinity of the grid 32. Provision for transferring energy into or out of the system is illustrated as made with the coupling loop 3E. The system can radiate through the hole 31 when this hole is provided. The operation of the arrangement shown in Figure 5 follows the theory already presented. In series with the battery 2| there is shown a source of alternating voltage 38 which when operating superimposes an alternating voltage on the direct accelerating voltage for modulating pur-f poses. This alternating voltage may be used to change the adjustment indicated by Fig. 3D in which the bunched electrons can be caused to reach grid 32 either when at minimum velocity or maximum velocity, as before described. This is useful in super-regenerative arrangements. By this method the oscillations of the system can be alternately started and stopped. In shifting to the adjustment in which the electrons reaching grid 32 are at high velocity the oscillations are stopped quickly because energy is taken from the circuit by the electron beam. This is equivalent to a large suddenly applied load for stopping oscillation, a feature which is not available in other types of oscillators.

Alternative forms of our invention are shown in Figures 6A, 6B, 6C, 6D, 7A, 7B and 7C. Figure 6A shows the development of a right circular cylinder into a form suitable for our invention. In the diagrams lines have been drawn to indicate qualitatively the electric lines of force. Fig. 6A, the lines of electric force 5D of the electromagnetic field are shown parallel to the axis of the cylinder. Thus the field may be said to be symmetrical in space. In other figures, however, the space-resonant device isl shown nonsymmetrical about a plane between the grids 24 and 25 perpendicular to the axis of the electric field to render the electric field component of the electromagnetic field substantially stronger at the grid 25 than at the grid 24.

Fig. (5B is derived from Fig. 6A by making the top of the cylinder convex at 52 and the bottom concave at 54, as viewed from the outside. The resulting lines of force 56 converge from the convex top 5.2 toward the concave bottom 54. The spacing between the lines of force 56 at a particular point is inversely proportional to the strength of the electric field at that point. The

Fig. 6C is derived from Fig. 6A by increasing or decreasing the diameter of one of the ends.

The lines of force 58 are therefore of a nature similar to the lines of force 55 of Fig. 6B. The strength of the field at the smaller end 60 is smaller than the strength of the eld at the larger end 52.

Fig. 6D is derived by combining the modifications of Figs. 6B and 6C. The corresponding lines of force 54 diverge a little more strongly than the lines of force 56 and 58. These arrangements of Figs. 6B, 6C and 6D increase the field intensity at one end relative to the intensity at the other over what is obtained with the cylindrical arrangement of Fig. 6A. This is desirable for practical purposes although our invention will operate with a right cylindrical space-resonant device with flat ends, as in Fig. 6A. For practical operation we have computed that this form will operate with an electron beam voltage of 100,000 if the ratio of the height of the cylinder to its diameter is about one to three. This form has the disadvantage of requiring a comparatively large electrcn current for operation.

A sphere as shown in Fig. 7A can be used in our invention but it requires such high voltages and currents for operation and the efiiciency is so low thatv it is not considered a practical form.

The hemisphere shown in Figure 7B is a practical form operating with voltages at 40,000 and f currents as low as about 50 milliamperes. This is because the lines of electric force 65 of Fig.

7B are considerably closer together at the plane boundary 58 than at the spherical boundary 1|).

This advantage is not obtained with the lines of force 12 of Fig. 7A. The sphere deformed as shown in Fig. 7C with sharp internal projection 14 gives a good field intensity but the use of a point is undesirable because of the small area v presented to the electron beam. Rounding the point to get more area for the beamreduces the field intensity so much that the arrangement is .not very desirable.

Figure 8 shows an embodiment of our invention possessing advantages of extreme simplicity.

In it anl oscillating circuit is provided by two i circular surfaces 4| and 42 and a conical connecting surface 43. where surface 4| is connected to it there is an annular insulated capacitive joint 44, across which is applied a direct current potential difference supplied by a battery 45. The battery 45 serves the same function as the batteries 35 `and 4| of Fig. 5. Attached to the inner face of surface i The operation of this embodiment is basically as has been described before, but in this arrangement the discontinuity of eld where the electrons enter it is at the surface of the emitter instead of at a grid. The direct current field is completely superimposed on the alternating cur-l In this surface preferably The emitter 45 is supported f rentv fieldqor the system? The electrons are" stopped' at the discontinuity existing inthe field'- Where it is bounded by the surface 42. By making theJjoint 44 airtight the structurecan be entirely application of Swell known electromagnetic theory. augmented by the mathematical development We have presented.

The-'application of the .present invention to uses as an amplien detector, oscillator, or in other Ways canabe accomplished With'referenceto the above-mentioned patents and copending applications...-Which showin detail how to 'apply the klystron-rfor these purposes.

klystroncan be donewith the Velectron'beam where itleaves -tlievsecond grid-of the monotron It -isfnotto be ex'l'oectedrthat the'monotron will Eachl has certainadvantage's rthat-will be apparent'todisplacefthe fklystr'on in all applications.

those A`skilled finnthe art. The simplicity off'the monotron krecommends it particularly for# applicationsi'where the lexibilityof the klystron-is not="neede'dv,`v as 'in some types rof oscillators.

Hav-ing described our invention `what we claim is-z'` 1.? Theirnethod of exciting a resonant 'circuit hav-ing 'an enclosed-electromagnetic eld. which consists 'Jefi causing a 'streami'of electrons to enter a. regien substantially--enclosed and containing the' oscillating `electromagnetic iield of saidcir-y cuit andto passthroughl it, causing'the electrons to b'e-isubjected to alternate increases and decreaseso'f speed in the direction-of travel thereof while'in said'rregion, and causing'them toleave saidregionI with less energy than they had when they enteredit, scz'dfildhaving a predetermined electromagnetic field 'intensity at the Zocatio'J/LVv where said electrons first enter IihenfZuen-ce of sazdirieldgand having a stronger field intensity where electrons leave the influence of said field,u thus sustaining oscillation of the'circut.

[2."The-'method of excitinga resonant circuit' Which-'consists of causing a stream` 'of electrons to enter Vthe oscillating electromagnetic eld of said scircuit in a region that is substantially enclosed, causing the electrons to be subjected Vto alternate increases and decreases of speedfin the direction of travel thereof in the eld, andvcausingl them to `leave the i'leld with less energy, in the aggregate, than they had when they entered it, thus delivering energy to the electromagnetic eld andsustaining oscillation of the circuit] v [3. The method of exciting a resonant circuit which consists of causing a stream of electrons to enter a region of standing electromagnetic waves that is substantially enclosed througha iield discontinuity at the boundary of said region, causing the electrons while in said region to interact with the eld ofthe circuit toalternatelyincrease and decrease the speeds of the electrons inthe direction of travel thereof, and causing the electrons to leave the region through another ld discontinuity vwith reduced energy, thus `de- Ingeneral-fanything Y thatcan-be done withthe electron beam leaving a liveringenergy toithe electromagnetic field and@ sustaining th'e oscillation offthecircuit'iA 4.- Tne method of Vabsorbing energyffromf-aresonant circuit whichA consists of f'causingfeleo i tronsitoenter a eld of StandingelectromagneticwavesV 'that is substantially enclosed 'through24a-' field :discontinuity atthe boundary thereof ,ieause` ing lthe electrons While 1in saidr` eldto i interact; withthesame and causing theelectrons to leave 'the-@Held through Ya iield discontinuityat Iftirnes'i when their energy is`- greatert-,thanifthe initiale energy.

-5.` An electromagnetic oscillator 1comprising.a,. hollow member providinga chamberah-aving con` ducting innerwall surfaces and adapted. for... containingk a resonant oscillating ..electromag... netic field of predetermined orientation,.\and

having la frequencyfof oscillation determined ,by the dimensionsvof said chamber, means fo'rpro--A looting "a stream of yelectrons substantiallylineally'gthrough. the chamber for. establishing and maintaining said iield, said-'member 'beingof diierent Vproportions vat 4the .places Where ther.

electron stream enters the fleldandQWhereY it rvleaves,theheld-to render the iield-Fat the y.first-1 named.V place lessv intense than the Vfield. at the second-'named place.

6..A'n, electromagnetic oscillator comprisinga v section of an approximately. sphericaloshell, a

hollow conical member, avsection .of aisrnaller-Y sphere placed Ainside l the shell. andwconnected with 'the shell by Ysaid Vconical member, the shell,

the smaller sphere.sectionVandfconical member. together forming aresonant chamber, saidfsri'ell` having a'gridfor admitting electronslrintothe chamber at predetermined orientationfor ,prof

ducing therein lthe. oscillating.electromagneticl ent points along the aX-is of the=streamsothat theelectric component of .said ,.eldvis stronger.

saidfcavity resonator meansthanit isatthe..

point of entry oi the electrons thereinto.

'8. A closed resonant circuitvconsisting-.of a'- conducting.. hollow substantially VTruste-conical member providing aV chamber,` one nwall of which chamber issaperturedf-.andconcave ltoward thef.

enclosed space,-the Yopposite wallof Awhich .chamber .irsalsoaperturedand convex toward lthe en-f closed space,.,andsmeans for. directing-astream of electrons .through saidchambervia said aper-f tured wal-1s.

9. A resonantcircuitcomprisinga:conducting Y shelly of rauoproximatelyspherical'iorm:with azreentrantWpart-presentng anapproximatelyfsphericall suriace within -the..shell, the shellfandreentrant part f together forming Yan electrically closed .boundary for fa containedf electromagnetic f [10." The method'ofvproducing electromagnetic oscillations .ina hollow'conductingfmember, comprisingprojecting a stream ofelectrons into said hollow conducting member,-sinusoidally altering the` velocity .of the electrons in the "direction of travelthereof insaid membery by ian-electro@ magnetic iieldresonant in said member, whereby`r travelingP electron groups-Sara formed :Within-:said i member. causing said groups to be alternately accelerated and decelerated by said electromagnetic field, and thereafter quickly removing said traveling electron groups from said field when they have been decelerated to a minimum velocitvJ 11. A method of controlling an electron stream that comprises causing electrons of the stream to enter a confined oscillating electromagnetic field and thereafter to travel in the field to cause the electrons thereafter to gain energy from and lose energy to the field, and causing the electrons to leave the eld at times when the field has gained energy on the whole from the electrons, said field having a predetermined electromagnetic yield intensity at the location where said electrons first enter the influence of said field, cmd having a stronger field intensity where said electrons leave the influence of said field.

12. A method of controlling an electron stream that comprises establishing a resonant electromagnetic field having boundaries of different field intensities, and causing electrons of the stream to enter the eld through the boundary of lesser field intensity, to travel through the field, and to leave the field through the boundary of greater eld intensity.

[13. A method of controlling an electron stream during its passage through an oscillating electromagnetic iield having standing electromagnetic waves contained in an internally resonant conducting hollow body that comprises causing electrons of the stream to assume periodically varying velocities in a predetermined region of the field, and causing the electrons thereafter to travel in the field beyond the said region to produce interaction at the resonant frequency of the field between the electrons of the stream iand the field to cause the electrons of the stream, as they pass through the field, to become concentrated in groups in. a second predetermined region of the fie1d.]

[14. A method of controlling an electron stream during its Ipassage through an oscillating electromagnetic field having standing electromagnetic waves contained in an internally resonant conducting hollow body that comprises impartin'g to the electrons of the stream in a predetermined region of the iield increments and decrements of energy of the period of the field to cause the electrons of the stream to assume periodically varying velocities, and causing the electrons thereafter to travel in the field beyond the said region to produce interaction at the resonant frequency of the field between the electrons of the stream. and the field to cause the electrons f of the stream, as they pass through the field, to become concentrated in groups in a second predetermined region of the field] [15. A method of controlling an electron stream during its passage through an oscillating electromagnetic field having standing electromagnetic waves contained in an internally resonant conducting hollow body that comprises imparting to the electrons of the stream in a predetermined region of the field increments and decrements of energy of the period of the field to cause the electrons of the stream to assume periodically varying velocities, causing the electrons thereafter to travel in the field beyond the said region to produce interaction at the resonant frequency of the field between the electrons of the stream and the iield to cause the electrons of the stream, as they pass through the field, to become concentrated in groups in a second predetermined region of the eld, and imparting to the electrons 22 individually in the second region greater incred ments and decrements than in the first-named predetermined region, with the decrements exceeding the increments] [16. A method of controlling an electron stream during its passage through an oscillating electromagnetic eld having standing electromagnetic Waves contained in an internally resonant conducting hollow body, the said hollow body containing also a substantial magnetic field component, the said method comprising causing elec# trons of the stream to assume periodically varying velocities in a predetermined region of the field, and causing the electrons thereafter to travel in the eld beyond the said region to pro-` duce interaction at the resonant frequency of the field between the electrons of the stream and the iield to cause the electrons of the stream, as they pass through the field, to become concentrated in groups in a second predetermined region of the field] A [17. A method of controlling an electron stream during its passage through an oscillating electromagnetic field having standing electromag` netic Waves contained in an internally resonant conducting hollow body that comprises passing an electron stream having a substantially uniform distribution in time from outside the body i'nto and through the field, and regulating the time of flight of the stream in the eld to produce interaction at the resonant frequency of the field between the electrodes of lthe stream and the field to cause the electrons of the stream, during their travel through the field, to deliver energy to the field at the resonant frequency of the field thereby to excite and maintain electromagnetic resonance in the field at the resonant frequency of the field] [18. A method of exciting a resonant circuit having an electromagnetic field in a substantially enclosed region that comprises causing a stream of electrons to enter into and to travel in the region, increasing and decreasing the speed of the electrons in the direction of travel thereof during their travel in the region, and causing the electrons to leave the region with less energy than they had when they entered it, thus sustaining oscillation of the circuit] [19. Apparatus foi1 generating alternating-current energy having, in combination, a space-resonant device having a. bounding surface, means for passing an electron stream through a portion of the bounding surface into the spaceresonant device, said device being of such proportions and the electrons of said stream having such velocities that a resonant oscillating electric field is established in the space-resonant device to cause the electrons to assume in a predetermined region of the field near the said portion of the bounding surface periodically varying speeds of the frequency of the field, in the direction of travel of the electrons, thereby to cause the electrons to become concentrated in groups during their further travel in the eld, and to cause the electron groups to leave the field at another portion of the bounding surface to lcause the electrons of the groups to transfer energy i ing, in combination, a space-resonant device, and

means for passing an electron stream into the space-resonant device to establish an oscillating resonant electromagnetic field in the space-resonant device, the dimension of the` space-resonant devicein the direction of-travel of the electron stream: and the resonant frequency-of the v ield being so related to the velocity of the electron stream in 4the'space-resonant device as to cause the .fieldto. abstract energyV rfrom l the electron stream] [21.` Apparatus of Athe character'descri-bed'having, in combination', a space-resonant device, and means `for passing-an electron streamrinto vthe space-resonant device to establish an oscillating resonant electromagnetic. field in the space-resonantIdevice, the dimension of the space-resonant devicefin the directionof travel of the electron stream and thefresonantfrequency-of the -eld being 'so related to the velocity'of vthe electron stream in the space-resonant device as to cause the electrons, when-in the space-resonant device, frstftof assume gperiodically varying velocities as a lfunction of the timeof entry into the spaceresonant device, secondly, to cause the faster electronswto gain upon the slower electrons to cause the electrons to become concentrated in groups `within the space-resonant device, and thirdly, to #cause thegroups'Y to leave the elcl with: lessl `energy than when the electrons entered]theeld, thereby to transfer energy to the field".

. [22a-Apparatus of the character described having, in combination, a space-resonant device, means for-passing an electron stream into 'the space-resonant device to establish an oscillating resonant electromagnetic i'ield in the space-resonant-device, the dimension of the space-resonant device in the .direction of travel of the electron stream and the resonant frequency ofthe field being. so related to the velocity off the electron stream in the space-resonant device as to cause the electrons, when in the' space-resonant device, first to assume periodically varying velocities as a function of the time `of entry into'the spaceresonant device, secondly, to cause the faster electrons to. gain'upon the slower electrons to cause .the electrons to become concentrated in groups. within the space-resonant device, land thirdly, to cause the groups to leaveI the 'eld with less energy than when the electrons entered the field, and means for-extracting energy from the field] [23. Apparatus of the character described having, in combination, a space-resonantV device having a boundingY surface, and means for passing anV electron stream through a portion of the bounding surface finto the space-resonant `device to establishan oscillating resonant electromagnetic field in the space-resonantdevice, the dimension of the space-resonant device inthe direction-,of travel of the electron stream and the resonant frequency of the field being so related to thefvelocity of the electron stream in the space-resonant device as :to cause the electrons,- whenin'the space-resonant device, first to assume in a'predetermined" region oflthe field near the saidf bounding surface periodically varying velocities having the frequency of the eld as a function of Vthe time' of entry into vthe yspaceresonantv device, second-ly, 'to cause the faster electrons to gain upon the slower electrons to cause the electrons to becomeconc'etrtrated Lin groups .during theirfurther travel in the field,v and thirdly, to cause the groups to leave Ythe eldat another portion of the boundingV surface with lessA energyl than Y when the electronsv 'entered' the eld, thereby-to transfer .energy to the field] ,Y [24.Apparatus1f'of f the .character `described having, in combination, a space-resonant device having an apertured wall, and means for-passingy anfelectronlstream into the'space-resonant device :through'thefapertured wall to establish an oscillating resonant electromagnetic iield in the spaced-*resonant devicegthe dimension of the spaceresonantidevice-dn the'direction of travelof the electronfstream andthe resonant frequency of the feld 'being Sol-related to the velocity of the electron stream in the space-resonant device as tofcause: theY electrons, when in vthe space-resonant device, 'first to assume-periodically varying velocities `as a function of the time of entry into the space-resonant device, secondly, toA cause the faster electrons to gainupon vthe slower electrons tov-cause the electrons to become concentrated in groupsewithin the Vspace-resonant device, kand thirdly, lto cause :the groups to leave the field withV less energy than whenthe electrons entered the-held, vthereby to transfer .energy to the field] |225.V Apparatus' o'frthe character described having, in combination, a space-resonant device having an: apertured wall', andmeans. for passing an electron stream into the Aspace-resonant device toceatablishyan voscillating resonant electromagnetic field in the space-resonantdevice and then out otfthe field through the apertured wall, the dimensioncof-.the space-resonant device in the direction of travelof thek electron stream and the-v resonantl frequency, of. the. iield being so related` yto-v-the'velocity yofthe electron stream in the-'space-resonant device as to cause the electrons,when inthe space-resonant device, first to assume periodically varying velocities as a functionof the timeof entry into the space-resonant device, secondly,"to cause the faster electrons to gain fupcn the7 slower electrons to cause the electrons tobecome Iconcentrated in groups withinfthegspace-resonant device, and' thirdly, to cause the groupsI to leave the field throughA the apertured wall with less energy than when the electrons entered the' ii'eld', thereby to transfer energy ito the held] [26., Apparatus of "the character described hayingpin combination, a space-resonant device,

. means forA passingran electron stream into the space-resonant device to establish an oscillating resonanty electromagnetic field inthe space-resonant device,l the dimension of the space-resonant device'in the direction of travel of the electron stream. and the resonant frequency of the i'eld being aso-f relatedy tothe Velocity of theV electron stream vin the space=resonant device as to cause the electrons, when'inthe space-resonant device, first ftoassumewperodically varying velocities as a functionof the time. of entry into the spaceresonant device, secondly, to cause the faster electrons to gain upon the slower electrons to cause therirelectrons I*to :become concentrated :in gro-ups within thecsspace-resonant device, and' thirdly, to cause vthe groups to leave the neld with less energy :than .iwhenathe electrons ventered the field, therebyljto vtransfer energy to the field, and means forsuperimposing a non-oscillating electric eld upontheelectromagnetic field' in the space-resonantdevice] f[2.7;gApparatus-othe described hayinggi'n combination, a space-resonant device, meansforpassing an electron stream into the space-resonant device `to establish an oscillating resonant.electromagnetic iield in the space-res- 75 tron stream in the space-resonant device as to cause the electrons, when in the space-resonant device, irst to assume periodically varying velocities as a function of the time of entry into the space-resonant device, secondly, to cause the faster electrons to gain upon the slower electrons to cause the electrons to become concentrated in groups within the space-resonant device, and thirdly, to cause the groups to leave the field with less energy than when the electrons entered the iield, thereby to transfer energy to the field, and means for superimposing upon the electromagnetic field in the space-resonant device a eld of frequency different from the irequency of the electromagnetic eldJ [28. Apparatus of the character described having, in combination, a space-resonant device having an inner evacuated portion and a surrounding non-evacuated portion separated by a dielectric boundary, and means for passing an electron stream into and through the evacuated portion of the space-resonant device to establish an oscillating resonant electromagnetic eld in the space-resonant device, the dimension of the space-resonant device in the direction of travel of the electron stream and the resonant frequency of the field being so related to the velocity of the electron stream in the space-resonant device as to cause the electrons, when in the spaceresonant device, first to assume periodically varying velocities, secondly, to cause the faster electrons to gain upon the slower electrons to cause thelelectrons to become concentrated in groups Within the space-resonant device, and thirdly, to

cause the groups to leave the field with less en ergy than when the electrons entered the neld, thereby to transfer energy to the iieldf 29. A closed resonant circuit comprising a conducting hollow substantially frusto-conieal chamber having an apertured end wall, and means for directing a stream of electrons into the chamber through the apertured end wall.

.30. A closed resonant circuit comprising a conducting hollow substantially frusto-conical chamber the small end Wall of which is apertured, and means for directing a stream of electrons into the chamber through the apertured end Wall.

31. Means for converting the kinetic energy of electrons in an electron stream into high frequency electromagnetic energy comprising a hcllow conducting member having two perpendicular axes and being non-symmetrical with respect to one of said axes, whereby the electric cornponent of an electromagnetic eld resonant therein converges toward one portion of the inner wall thereof and diverges therefrom toward an opposite portion of the said wall, and means for projecting a stream of electrons through said hollow conducting member from said opposite wall portion substantially along the other of said axes to the Wall portion toward which said component converges.

WILLIAM W. HANSEN. RUSSELL H. VARIAN.

No references cited. 

